Energy Efficiency That Even the Human Brain Would Envy... Artificial Synapse Developed from Crab and Soybean-Based Materials

UNIST Team Led by Ko Hyunhyup Develops High-Performance, Biodegradable Artificial Synapse
Robotic Arm Instantly Releases Hot Objects by Reflex; Published in Nature Communications

An artificial synapse that consumes even less energy than a human brain synapse has been developed.

A quiet revolution led by waste and plants has begun. Artificial synapses made from materials derived from nature have easily surpassed existing limitations, opening up new possibilities for neural network technology that minimizes power consumption.

This artificial synapse is made from crab shells, soybeans, and plant stem extracts. After use, it can be completely decomposed in soil, which is expected to help address the problem of electronic waste.

On December 9, the research team led by Professor Ko Hyunhyup in the Department of Energy and Chemical Engineering at UNIST announced that they had developed a high-performance artificial synapse made solely from eco-friendly, biodegradable materials.

Research team (from left) Professor Ko Hyunhyup, Researcher Jang Yujin (first author), Dr. Na Sangyun (co-first author), Dr. Noh Yungu (co-first author). Provided by UNIST

A synapse is the point at which signals are transmitted between neurons in the brain. Neurotransmitters released from the presynaptic neuron bind to receptors on the postsynaptic neuron, continuing the electrical signal.

The artificial synapse developed by the research team has a sandwich-like structure, with an ion-binding layer sandwiched between ion-active layers. When an electrical stimulus is applied to the ion-active layer, sodium ions-which act as neurotransmitters-are released and bind to the ion-binding layer, which serves as the receptor. Even after the electrical stimulus disappears, some ions remain in place, adjusting the output intensity of the next signal. This mechanism closely resembles the process in human synapses, where neurotransmitters bind to receptors and some remain to strengthen memory.

This artificial synapse triggers signal transmission using only 0.85 femtojoules (10?¹? J) of energy, which is even less than that of human synapses. Even highly energy-efficient human synapses consume about 1 to 10 femtojoules (2.4 × 10?¹? to 2.4 × 10?¹? calories), but this artificial synapse uses less energy than that.

It also recorded a long-term memory retention time of 5,994 seconds (about 100 minutes), the longest ever reported for a biodegradable artificial synapse. The longer the ions remain between the ion-binding and ion-active layers, the greater the long-term memory retention time.

Additionally, both the ion-active and ion-binding layers that make up the artificial synapse are eco-friendly and biodegradable, allowing them to fully decompose in soil within 16 days. The ion-binding layer is made of cellulose acetate processed from plant stems, while the ion-active layer is a composite polymer material made from chitosan extracted from crab shells and guar gum extracted from soybeans.

The research team also created a "biomimetic reflex robotic hand" that uses the artificial synapse to learn and remember thermal stimuli, enabling it to respond to dangerous situations. When the temperature rises, ion movement within the synapse becomes more active, increasing the efficiency of signal transmission, and this change is retained in the artificial synapse. As a result, when dangerous levels of heat are detected again, the amplified signal is sent directly to the motor that moves the hand, allowing the robot to instantly release a hot object, mimicking a reflex action.

Biomimetic reflex system combining artificial synapses and thermal sensing robot actuation.

This research was jointly authored by Researcher Jang Yujin, Dr. Na Sangyun, and Dr. Noh Yungu from the Department of Energy and Chemical Engineering. The research team explained, "Biodegradable materials are generally vulnerable to moisture and heat, but we addressed this by designing the materials to form strong hydrogen bonds. The synapse structure is also simple, making it easy to manufacture."

Professor Ko Hyunhyup emphasized, "It is significant that we have simultaneously solved the long-standing challenges of ultra-low power consumption, long-term memory retention, mechanical stability, and complete biodegradability in artificial synapse technology. This will be an important turning point in laying the foundation for the development of sustainable next-generation neuromorphic devices."

This research was supported by the Individual Basic Research Program (Mid-Career Researcher Program) of the National Research Foundation of Korea and was published on November 27 in Nature Communications, a sister journal of the world-renowned journal Nature.

This content was produced with the assistance of AI translation services.